git/lockfile.h, branch v2.10.2

mingw: ensure temporary file handles are not inherited by child processes

2016-08-23T16:09:55Z

When the index is locked and child processes inherit the handle to said lock and the parent process wants to remove the lock before the child process exits, on Windows there is a problem: it won't work because files cannot be deleted if a process holds a handle on them. The symptom: Rename from 'xxx/.git/index.lock' to 'xxx/.git/index' failed. Should I try again? (y/n) Spawning child processes with bInheritHandles==FALSE would not work because no file handles would be inherited, not even the hStdXxx handles in STARTUPINFO (stdin/stdout/stderr). Opening every file with O_NOINHERIT does not work, either, as e.g. git-upload-pack expects inherited file handles. This leaves us with the only way out: creating temp files with the O_NOINHERIT flag. This flag is Windows-specific, however. For our purposes, it is equivalent to O_CLOEXEC (which does not exist on Windows), so let's just open temporary files with the O_CLOEXEC flag and map that flag to O_NOINHERIT on Windows. As Eric Wong pointed out, we need to be careful to handle the case where the Linux headers used to compile Git support O_CLOEXEC but the Linux kernel used to run Git does not: it returns an EINVAL. This fixes the test that we just introduced to demonstrate the problem. Signed-off-by: Ben Wijen Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

lockfile: remove function "hold_lock_file_for_append"

2015-08-28T18:32:01Z

With 77b9b1d (add_to_alternates_file: don't add duplicate entries, 2015-08-10) the last caller of function "hold_lock_file_for_append" has been removed, so we can remove the function as well. Signed-off-by: Ralf Thielow Acked-by: Jeff King Signed-off-by: Junio C Hamano

tempfile: a new module for handling temporary files

2015-08-10T19:57:14Z

A lot of work went into defining the state diagram for lockfiles and ensuring correct, race-resistant cleanup in all circumstances. Most of that infrastructure can be applied directly to *any* temporary file. So extract a new "tempfile" module from the "lockfile" module. Reimplement lockfile on top of tempfile. Subsequent commits will add more users of the new module. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile: add accessor get_lock_file_path()

2015-08-10T19:57:14Z

Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile: add accessors get_lock_file_fd() and get_lock_file_fp()

2015-08-10T19:57:14Z

We are about to move those members, so change client code to read them through accessor functions. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile: move documentation to lockfile.h and lockfile.c

2015-08-10T19:57:14Z

Rearrange/rewrite it somewhat to fit its new environment. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile: allow file locking to be retried with a timeout

2015-05-14T21:51:08Z

Currently, there is only one attempt to lock a file. If it fails, the whole operation fails. But it might sometimes be advantageous to try acquiring a file lock a few times before giving up. So add a new function, hold_lock_file_for_update_timeout(), that allows a timeout to be specified. Make hold_lock_file_for_update() a thin wrapper around the new function. If timeout_ms is positive, then retry for at least that many milliseconds to acquire the lock. On each failed attempt, use select() to wait for a backoff time that increases quadratically (capped at 1 second) and has a random component to prevent two processes from getting synchronized. If timeout_ms is negative, retry indefinitely. In a moment we will switch to using the new function when locking packed-refs. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile: remove unable_to_lock_error

2014-10-15T17:47:27Z

The former caller uses unable_to_lock_message now. Signed-off-by: Jonathan Nieder Reviewed-by: Ronnie Sahlberg Signed-off-by: Junio C Hamano

fdopen_lock_file(): access a lockfile using stdio

2014-10-01T21:08:10Z

Add a new function, fdopen_lock_file(), which returns a FILE pointer open to the lockfile. If a stream is open on a lock_file object, it is closed using fclose() on commit, rollback, or close_lock_file(). This change will allow callers to use stdio to write to a lockfile without having to muck around in the internal representation of the lock_file object (callers will be rewritten in upcoming commits). Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano

lockfile.h: extract new header file for the functions in lockfile.c

2014-10-01T20:56:14Z

Move the interface declaration for the functions in lockfile.c from cache.h to a new file, lockfile.h. Add #includes where necessary (and remove some redundant includes of cache.h by files that already include builtin.h). Move the documentation of the lock_file state diagram from lockfile.c to the new header file. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano